• Korean Management Science Review
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• v.27 no.2
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• pp.21-29
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• 2010

We consider an economic approach for spectrum operations in mobile networks. We present the investment function of base stations according to the number of FAs assuming the linearity of cell splitting. We show that there is an economic amount of spectrum which corresponds to the optimal number of FAs that minimizes the investment. We analyze the impact of the cost structure and the traffic distribution in base stations on the economic amount of spectrum. This paper is applicable to an economic spectrum operation for mobile operators. In addition, the national regulatory authority can use the economic amount of spectrum as the minimal amount for spectrum allocation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.2
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• pp.29-35
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• 2013

For the purpose of designing and applying optimum surge protection, one of the essential points is to take into account the energy coordination between cascaded surge protective devices(SPDs) and it is important to obtain an acceptable sharing of the energy stress between two cascaded SPDs. In this paper, in case of two voltage-limiting SPDs connected in parallel, the amount of splitting impulse current and energy that flow through each SPDs is investigated as a function of the protective distance. As a result, the energetic coordination between cascaded SPDs is strongly dependent on the voltage protection level of SPDs and the protective distance. It was confirmed that the sharing of the energy between two cascaded SPDs and the limited voltage levels are appropriate when the voltage protection levels of both upstream and downstream SPDs are the same.

• Computers and Concrete
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• v.8 no.3
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• pp.243-278
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• 2011

The paper presents simulations of the Brazilian test using two numerical models. Both models are regularized in order to obtain results independent of discretization. The first one, called gradient damage, is refined by additional averaging equation which contains gradient terms and an internal length scale as localization limiter. In the second one, called viscoplastic consistency model, the yield function depends on the viscoplastic strain rate. In this model regularization properties are governed by the assumed strain rate. The two models are implemented in the FEAP finite element package and compared in this paper. Parameter studies of the split test are performed in order to point out the features of each model.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.156-157
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• 2003

A simple method is proposed to split the flux vector of the Euler equations by introducing two artificial wave speeds. The direction of wave propagation can be adjusted by these two wave speeds. This idea greatly simplifies the upwinding, and leads to a new family of upwind schemes. Numerical flux function for multi-dimensional Euler equations is formulated for any grid system, structured or unstructured. A remarkable simplicity of the scheme is that it successfully achieves one-sided approximation for all waves without recourse to any matrix operation. Moreover, its accuracy is comparable with the exact Riemann solver. For 1-D Euler equations, the scheme actually surpasses the exact solver in avoiding expansion shocks without any additional entropy fix. The scheme can exactly resolve stationary contact discontinuities, and it is also freed of the carbuncle problem in multi­dimensional computations.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.408-415
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• 1997

Bond strength of reinforcing bar to high-performance concrete using Belite cement is explored using beam end test specimen. The key parameters for the bond test are slump of concrete, top bar effect, and strength of concrete in addition to concrete covers. Specimen failed in the typical brittle bond failure splitting the concrete cover as the wedging action. The test results show that for the group with portland cement I using superplasticizer additional slump does not decrease the bond strength of the top bar is less than bond strength of bottom bar, but the top bar factor satisfy the modification factor for top reinforcement. The result also show that bond strength is function of square root of concrete compressive strength and cover thickness. More detailed evaluation will be conducted from the test specimen with high strength concrete using the belite cement.

• Journal of the Society of Naval Architects of Korea
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• v.41 no.4
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• pp.17-29
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• 2004

Internal waves are computed using a ghost fluid method on an unstructured grid. Discontinuities in density and dynamic pressure are captured in one cell without smearing or oscillations along a multimaterial interface. A time-accurate incompressible Navier-Stokes/Euler solver is developed based on a three-point backward difference formula for the physical time marching. Artificial compressibility is introduced with respect to pseudotime and an implicit method is used for the pseudotime iteration. To track evolution of an interface, a level set function is coupled with the governing equations. Roe's flux difference splitting method is used to calculate numerical fluxes of the coupled equations. To get higher order accuracy, dependent variables are reconstructed based on gradients which are calculated using Gauss theorem. For each edge crossing an interface, dynamic pressure is assigned for a ghost node to enforce the continuity of total pressure along the interface. Solitary internal waves are computed and the results are compared with other computational and experimental results.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.489-492
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• 2004

Compressive strength of self-compacting concrete with waste concrete powder(SCCWCP) linearly decreased as the containing ratio of WCP increas. When granulated blast furnace slag(SG) was contained for improving the rheological properties of SCCWCP, compressive strength of concrete with $15\%$ SG and $15\%$ WCP was increased in comparison with that of concrete with $30\%$ WCP. Splitting tensile strength of SCCWCP higher increased than that of CEB-FIP at same compressive strength. Relationship between compressive strength and elastic modulus of SCCWCP indicated a similar function with CEB-FIP fuction.

• Bulletin of the Korean Chemical Society
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• v.15 no.3
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• pp.198-204
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• 1994

Chemical shifts in aqueous sodium dodecylsulfate(SDS) micellar solution solublizing phenol, catechol, resorcinol, hydroquinone have been measured to investigate solubilization properties. Proton nuclear magnetic resonance frequencies of solubilizates as well as those of the ${\alpha}$-methylene, middle methylene and terminal methyl of SDS shift linearly as a function of solubilizate concentration. From the plots of observed chemical shift (v) vs solubilizate concentration, slope (a) and solubilizate free chemical shift ($v_0$) are obtained. They are very informative to solubilization site of the systems. Catechol and phenol solubilized SDS and catechol solubilized dodecylpyridinium chloride(DPC), dodecyltrimethylammonium bromide(DTAB) systems are studied using the same method to compare head group effect and middle methylene proton signal splitting. It is proposed that phenol and catechol are inserted into micellar interior and the number of methylenes assigned to the higher field peaks is 5.0${\pm}$0.5.

• Journal of applied mathematics & informatics
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• v.41 no.2
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• pp.321-330
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• 2023

Let G = (V, E) be a graph. Consider the group S₃. Let g : V (G) → S₃ be a function. For each edge xy assign the label 1 if ${\lceil}{\frac{o(g(x))+o(g(y))}{2}}{\rceil}$ is odd or 0 otherwise. g is a group S₃ mean cordial labeling if |v_g(i) - v_g(j)| ≤ 1 and |e_g(0) - e_g(1)| ≤ 1, where vg(i) and e_g(y)denote the number of vertices labeled with an element i and number of edges labeled with y (y = 0, 1). The graph G with group S₃ mean cordial labeling is called group S₃ mean cordial graph. In this paper, we discuss group S3 mean cordial labeling for star related graphs.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.3
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• pp.339-344
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• 2014

Purpose: This study relates to the development of the day and night scope using the reflecting surface of a BS (beam splitting) prism. Methods: We have placed the LCD panel and the dot reticle generator to the top and bottom of the reflecting surface of the BS prism, and have placed a reflector, which is designed to doublet type, in the front of the BS prism. Doing so, we have developed a new type of day and night scope, which is able to image the virtual image of dot reticle from the dot reticle generator to the direction of the observer, to make the observer survey the peripheral information of the outside target by 1x magnification, and to make the observer survey the image of the LCD panel directly. Results: We could develope a new type of day and night scope, which has the function of night scope as thermal image display device at night time and the function of day scope as dot sight at day time, by letting the reflective surface of the BS prism have the role of dot sight which reflects the dot reticle and have the role of reflective optical system by which the observer surveys the night thermal image displayed in LCD panel. Conclusions: In this study, we have developed the new type of day and night scope which is able to play the role of the day or night scope selectively, combining the existing dot sight and the existing night scope by using the BS prism. By doing so, we could design and fabricate the new type of day and night scope with the BS prism which can further increase the rapidity of firing and provide more convenience in the mounting of a firearm than the detachable combination of an existing dot sight and an existing night scope.